Filling undercut areas of teeth relative to axes of appliance placement

ABSTRACT

The present disclosure provides computing device implemented methods, computing device readable medium, and molds for filling undercut areas of teeth relative to an axis of placement. Filling undercut areas of teeth relative to an axis of placement can include calculating an undercut area of a tooth relative to an axis of placement of part of a dental appliance over a number of teeth and a height of contour that is defined based on the axis of placement. Filling undercut areas of teeth relative to an axis of placement can also include filling in a part of the undercut area of the tooth with a virtual filler wherein the undercut is filled to within a threshold distance from the tooth that is defined relative to the axis of placement and the height of contour.

PRIORITY INFORMATION

The present application is a continuation of U.S. patent applicationSer. No. 15/182,171, filed Jun. 14, 2016 and issued as U.S. Pat. No.10,123,852 on Nov. 13, 2018, which is a continuation of U.S. patentapplication Ser. No. 13/680,888, now U.S. Pat. No. 9,364,296, filed onNov. 19, 2012, the contents of which are incorporated herein byreference.

BACKGROUND

The present disclosure is related generally to the field of dentaltreatment. More particularly, the present disclosure relates tomodifying digital images of teeth to improve fit of dental appliancesmade using the images.

Dental treatments can involve repositioning misaligned teeth andchanging bite configuration for improved cosmetic appearance and dentalfunction. Orthodontic repositioning can be accomplished, for instance,through a dental process that uses one or more removabletooth-positioning appliances for realigning teeth.

Such appliances may utilize a shell of material having resilientproperties, referred to as an “aligner” that generally conforms to apatient's teeth but is slightly out of alignment with the then currenttooth configuration. Placement of an appliance over the teeth canprovide controlled forces in specific locations to gradually move theteeth into a new configuration. The appliances can be semi-rigid,allowing for flexing of the appliances as the appliance is placed overthe teeth of a patient.

Placement of the appliance over the teeth can be affected by an undercutarea of a tooth of a patient. An undercut area of a tooth can include anarea of a tooth below a widest part of the tooth, which may or may notbe the height of contour of a tooth depending on the orientation of thetooth in the jaw, and extending toward the gingival line of the patient.In some instances, it can be difficult for a patient with insufficientor excessive undercut areas to secure the appliance over their teeth.For instance, an appliance placed on teeth of a patient withinsufficient undercut areas may slip off the patient's teeth in anundesirable fashion and/or at undesired times; and, an appliance placedon teeth of a patient with over-sufficient undercut areas may beextremely difficult to insert causing great discomfort and/or distortionin the appliance. How well an appliance is seated on the patient's teethcan be referred to as the degree of fit of the appliance. For situationswith excessive undercuts, it may be possible to fill an undercut area ofa tooth with a filler material prior to the impression of the teethand/or by blocking out the reference on the dental mold during theappliance fabrication process, so that the fit of the appliance isimproved (e.g., improving the retention of the appliance onto the numberof teeth). For insufficient undercuts, artificial undercuts may becreated by trimming away parts of the reference model and/or byphysically creating undercuts on the teeth. In any case, what istypically assumed is a single path of insertion (e.g., line of drawand/or axis of placement) and removal for a single appliance. In theevent of a rigid appliance, only a single path of insertion can exist.However, for semi-rigid flexible appliances, multiple paths of insertionand removal can exist, or at least difference paths of insertion andremoval for different portions of the appliance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates an example of a digital dental model according toone or more embodiments of the present disclosure.

FIG. 1B illustrates an example of multiple axes of placement of parts ofa dental appliance according to one or more embodiments of the presentdisclosure.

FIG. 2A illustrates an example of a height of contour and an undercutarea of a tooth that is defined based on an estimated axis of placementof part of a dental appliance according to one or more embodiments ofthe present disclosure.

FIG. 2B illustrates an example of a virtual filler filled in part of anundercut area of a tooth according to one or more embodiments of thepresent disclosure.

FIG. 2C illustrates an example of a dental appliance according to one ormore embodiments of the present disclosure.

FIG. 3 is a flow diagram illustrating an example of a method for fillingundercut areas according to one or more embodiments of the presentdisclosure.

FIG. 4 illustrates an example computing device readable medium 456having executable instructions that can be executed by a processor toperform a method according to one or more embodiments of the presentdisclosure.

FIG. 5A illustrates an example of a method for filling excessiveundercut areas on a dental mold according to one or more embodiments ofthe present disclosure.

FIG. 5B illustrates an example of a method for filling insufficientundercut areas on a dental mold according to one or more embodiments ofthe present disclosure

FIG. 6A illustrates an example of a tooth with insufficient undercutarea according to one or more embodiments of the present disclosure.

FIG. 6B illustrates an example of a dental appliance according to one ormore embodiments of the present disclosure.

DETAILED DESCRIPTION

Dental professionals typically create a treatment plan for a patient'steeth based upon their experience with certain features and/orcharacteristics of dental appliances in connection with the teeth inconsideration for treatment. In an ideal situation, the appliancecharacteristics are compatible with the condition of the teeth underconsideration for treatment. For example, a dental appliance to beplaced over a patient's teeth can be considered as part of a dentaltreatment plan. How well the dental appliance may fit over theparticular patient's teeth can be a consideration, which can include theseverity of undercuts and also the absence of important retentionelements needed for the planned appliance to stay in place.

Typically an undercut is the portion of the appliance which engages theteeth and resists removal of the appliance in the direction of the axisof placement (e.g., path of insertion and/or removal). Resistance toplacement occurs when the portion of the appliance which engages theundercut needs to first overcome the height of contour perpendicular tothe axis of placement of the appliance during the insertion process. Ifan appliance portion is narrow because of a large undercut, thenarrowness will need to stretch first in order to overcome the height ofcontour, thus making placement more difficult than if the undercut isless severe and the appliance is less narrow as a result. Undercuts forretaining a dental appliance therefore need to be sufficient to retainthe appliance on the teeth, but not excessive so as to prevent adequateinsertion or removal of the appliance.

Reducing undercut areas of teeth relative to an axis of placement of thedental appliance can be beneficial, for example, in that the reducedundercut areas can assist the patient in placing the dental applianceover the patient's teeth. This can be accomplished by filling inundercut areas of the actual teeth using block-out compounds (e.g., alight-cured resin) prior to taking an impression or scan of thepatient's teeth. Or, a model of the patient's teeth can have theundercuts blocked out either physically (e.g., with block-out compound)or digitally before any appliances are made from the patient's model.

The result of reducing excessive undercuts relative to an axis ofplacement can be an improved ease to fitting the dental appliance on theteeth while reducing stress on the dental appliance itself when tryingto place the dental appliance over the teeth of a patient. Excessiveforce is undesirable when placing or removing a dental appliance becausethe appliance may become permanently distorted or the patient mayexperience pain during the insertion/removal of the appliance.

An undercut area of a tooth relative to an axis of placement of a dentalappliance, as used herein, can include an area between a height ofcontour of the tooth relative to an axis of placement and the gingivasurrounding of the tooth. Reduced stress on the semi-rigid dentalappliance can result in less breakage and/or tears of the dentalappliance during its use and/or during its manufacture when theappliance is being inserted and removed from the reference model of theteeth. Furthermore, a dental appliance may be more comfortable for apatient when undercut engagement areas are optimized based oninformation regarding the axis of placement of the dental appliance. Thegoal is to create an appliance which is neither too loose nor toodifficult to place and remove, and to take advantage of the semi-rigidproperties of the appliance in order to allow multiple axis of placementto be considered based on how the appliance flexes during insertion andremoval from the teeth.

The present disclosure provides a computing device-implemented method,computing device readable medium, and mold related embodiments forfilling undercut areas of teeth. For example, one or more embodimentsinclude a non-transitory computing device medium having executableinstructions that can be executed by a processor to cause a computingdevice to perform a method, comprising calculating an undercut area of atooth relative to an axis of placement of a part of a dental applianceover a number of teeth and a height of contour that is defined based onthe axis of placement, and filing in a part of the undercut area with avirtual filler wherein the undercut is filled to within a thresholddistance from the tooth that is defined relative to the axis ofplacement and the height of contour. An artificial undercut may also becreated and/or introduced in situations where an insufficient undercutarea is present, accomplished by introducing a virtual object with atleast one dimension which increases until a threshold distance ispresent to ensure adequate device retention.

In the following detailed description of the present disclosure,reference is made to the accompanying drawings that form a part hereof,and in which is shown by way of illustration how a number of embodimentsof the disclosure may be practiced. These embodiments are described insufficient detail to enable those of ordinary skill in the art topractice a number of embodiments of this disclosure, and it is to beunderstood that other embodiments may be utilized and that changes maybe made without departing from the scope of the present disclosure.

As will be appreciated, elements shown in the various embodiments hereincan be added, exchanged, and/or eliminated so as to provide a number ofadditional embodiments of the present disclosure. In addition, as willbe appreciated, the proportion and the relative scale of the elementsprovided in the figures are intended to illustrate the embodiments ofthe present disclosure, and should not be taken in a limiting sense. Asused herein, “a”, “at least one”, and “a number of” something can referto one or more such things. Also as used herein, the designator “N”,particularly with respect to reference numerals in the drawings,indicates that a number of a particular features so designated can beincluded.

The figures herein follow a numbering convention in which the firstdigit or digits correspond to the drawing figure number and theremaining digits identify an element or component in the drawing.Similar elements or components between different figures may beidentified by the use of similar digits. For example, 106 may referenceelement “6” in FIG. 1B, and a similar element may be referenced as 206in FIG. 2C. As will be appreciated, elements shown in the variousembodiments herein can be added, exchanged, and/or eliminated so as toprovide a number of additional embodiments of the present disclosure. Inaddition, as will be appreciated, the proportion and the relative scaleof the elements provided in the figures are intended to illustratecertain embodiments of the present disclosure, and should not be takenin a limiting sense.

Although the overarching term “orthodontics” is used herein, the presentdisclosure is not so limited to treatments of an orthodontic nature. Thepresent disclosure may, for instance, relate to non-orthodontic dentaltreatment appliances. Dental treatment appliances and/or dentalappliances, as used herein, can include an appliance that is to beremoveably attached to teeth. For example, dental appliances can includeorthodontic appliances, surgical splints, bruxism appliances, TMJtreatment appliances, snap-on cosmetic dental appliances, removableprosthetics, and/or sleep apnea appliances, among many other removabledental appliances.

As an example, in cases of a flexible removable prosthetic (e.g.,partial denture), unlike rigid prosthetics which are designed for asingle axis of placement (e.g., path of insertion and/or removal), morethan one axes of placement may be available for a flexible prostheticdepending on the portion of the prosthetic being inserted and thesequence of the insertion. The present disclosure may be applied toensure that the insertion and/or removal of a flexible removableprosthetic is optimized for better retention and removal than what asingle axes of placement can afford.

Digital dental models from a scan of a patient's dentition can beprovided with computer-aided design and/or manufacturing systems,including tooth-treatment systems. A digital dental model representingan initial tooth arrangement may be obtained in a variety of ways.

For example, the patient's teeth may be imaged to obtain digital datausing direct and/or indirect structured light, X-rays (e.g.two-dimensional and three-dimensional X-rays), lasers, destructivescanning, computer-aided tomographic images or data sets, magneticresonance images, intra-oral scanning technology, photographicreconstruction, and/or other imaging techniques. The digital dentalmodel can include an entire mouth tooth arrangement, some, but not allteeth in the mouth, and/or it can include a single tooth.

A physical positive model and/or negative impression of the patient'steeth or a tooth may be scanned using an X-ray, X-ray imager, laserscanner, destructive scanner, structured light, and/or other rangeacquisition system to produce the initial digital dental model. The dataset produced by the range acquisition system may be converted to otherformats to be compatible with the software (e.g., executableinstructions) which is used for manipulating images within the data set,as described herein.

Referring now to FIG. 1A, there is illustrated an example of a digitaldental model according to one or more embodiments of the presentdisclosure. As described herein, a digital dental model 100 can beobtained prior to treatment or at an intermediate stage of treatment(e.g., before treatment has completed). The digital dental model 100 caninclude an initial position of a number of teeth 102-1, 102-2, 102-3,102-4, 102-5, 102-6, 102-7, 102-8, 102-9, 102-10, 102-11, 102-12 . . .102-N, 103. For instance the number of teeth 102-1, . . . , 102-N, 103can include a lingually displaced premolar and/or molar 103.

The digital dental model 100, as illustrated in FIG. 1A, can include atop-down view of a number of teeth 102-1, . . . , 102-N, 103. However,digital dental model embodiments of the present disclosure are not solimited to a top-down view. A digital dental model 100 can be viewed ina number of ways (e.g., side view, front view, three-dimensional view).

The digital dental model 100 in accordance with one or more embodimentscan include a digital dental model of a number of teeth 102-1, . . . ,102-N, 103 located on a lower jaw of a patient, upper jaw of a patient,and/or both. The number of teeth 102-1, . . . , 102-N, 103 in thedigital dental model 100 can include a tooth and/or a number of teethwith an undercut area relative to an axis of placement of a part of adental appliance over the number of teeth and a relative height ofcontour that is defined based on the axis of placement.

FIG. 1B illustrates an example 113 of multiple axes of placement 112,114, 116 of parts of a dental appliance 106 according to one or moreembodiments of the present disclosure.

Appliances can include any positioners, retainers, and/or otherremovable dental appliances for finishing and maintaining teethpositioning in connection with a dental treatment. These appliances maybe utilized by the treatment professional in performing a treatmentplan. For example, a treatment plan can include the use of a set ofappliances, created according to models described herein. Appliances, insome embodiments, can include flexible dental appliances which serve inpart as a prosthesis for esthetics and/or dental function.

An appliance (e.g., dental appliance 106 in FIG. 1B) can, for example,be fabricated from a polymeric shell, and/or formed from other material,having a cavity shaped to receive and apply force to reposition one ormore teeth from one teeth arrangement to a successive teeth arrangement.The shell may be designed to fit over a number of, or in many instancesall, teeth present in the upper and/or lower jaw.

A dental appliance is often positioned on a number of teeth in multiplesteps where a first part of the dental appliance is placed over a firstset of teeth and a second part is subsequently places over a second setof teeth. In such embodiments, the placement of each part may have adifferent axis of placement. When the appliance is removed, the removalof each part may have a different axis of removal. The removal axisand/or axes, in some embodiments, may not be the same as the placementaxis and/or axes. Nor does removal need to be in the same sequence asthe placement.

The embodiment of FIG. 1B illustrates multiple axes of placement 112,114, 116 of a dental appliance 106 and can include a defined estimatedpath of placement of a part of the dental appliance 106 over a number ofteeth. A vector representing the path of placement of a part of thedental appliance can include a line of draw of the dental appliance.

For instance, as discussed above, a dental appliance can have multipleaxes of placement. Multiple axes of placement can include axes ofplacement 112, 114, 116 of different parts of the dental appliance 106over the number of teeth. An axis of placement 112, 114, 116 can includeany direction of travel of an appliance as it is to be placed over oneor more teeth. A part of the dental appliance 106 can include ananterior region, a posterior right region, and/or a posterior leftregion, for example. In examples of the present disclosure, an axis ofplacement can include a buccal to lingual path and/or a lingual tobuccal path, among other paths.

In the some embodiments of the present disclosure, as illustrated inFIG. 1B, multiple axes of placement 112, 114, 116 can include two axesof placement of parts of a dental appliance 106 over a number of teethcan include a first axis of placement 112 of a first part of a dentalappliance 106 and a second axis of placement 114, 116 of a second partof a dental appliance 106. For example, the first part of the dentalappliance 106 can be placed over a number of teeth (e.g., a firstsub-number of teeth among the number of teeth) along the first axis ofplacement 112, and the second part of the dental appliance 106 can beplaced over a number of teeth (e.g., a second sub-number of teeth amongthe number teeth) along the second axis of placement 114, 116, and/orany combination thereof. A sum of the first sub-number of teeth and thesecond sub-number of teeth can include the number of teeth (e.g., atotal number of teeth of the patient that the dental appliance is to beplaced on), for instance.

The first axis of placement 112 can, for example, be with respect to ananterior path. As used herein, an anterior path can include placement ofan anterior part of the dental appliance 106 over one or more of apatient's incisor teeth and/or canine teeth. A second path 114, 116 caninclude a posterior path. As used herein, a posterior path can includeplacement of a posterior part of the dental appliance 106 over one ormore of a patient's premolar teeth and molar teeth. For instance, aposterior path can include a posterior right path and/or a posteriorleft path. Thereby, an anterior part of a dental appliance 106 can beplaced over the anterior teeth of a patient along a first axis ofplacement 112 and then a posterior part of the dental appliance 106(e.g., posterior right part and/or posterior left part of the dentalappliance) can be placed over the posterior teeth of the patient along asecond axis of placement 114, 116.

In accordance with some embodiments of the present disclosure, multipleaxes of placement 112, 114, 116 can include three axes of placement 112,114, 116, as illustrated in FIG. 1B. Three axes of placement can includea first axis of placement 112 of a first part of a dental appliance 106,a second axis of placement 114 of a second part of the dental appliance106, and a third axis of placement 116 of a third part of the dentalappliance 106. For example, the first part of the dental appliance 106can be placed over a number of teeth (e.g., a first sub-number of teethamong the number of teeth) along the first axis of placement 112, thesecond part of the dental appliance 106 can be placed over a number ofteeth (e.g., a second sub-number of teeth among the number of teeth)along the second axis of placement 114, the third part of the dentalappliance 106 can be placed over a number of teeth (e.g., a thirdsub-number of teeth) along the third axis of placement 116, and/or anycombination thereof. A sum of the first sub-number of teeth, the secondsub-number of teeth, and the third sub-number of teeth can include thenumber of teeth, for instance.

The first axis of placement 112 can include an anterior path, the secondaxis of placement 114 can include a posterior left path, and the thirdaxis of placement 116 can include a posterior right path, for example.Each axis of placement 112, 114, 116 can include a diagonal, a vertical,and/or a horizontal path in one or more dimensions from a buccal tolingual side of the sub-number of teeth and/or lingual to buccal side ofthe sub-number of teeth, for example. Thereby, an anterior part of adental appliance 106 can be placed over the anterior teeth of a patientalong a first axis of placement 112, then a posterior left part of thedental appliance 106 can be placed over the posterior left teeth of thepatient along a second axis of placement 114, and then a posterior rightpart of the dental appliance 106 can be placed over the posterior rightteeth of the patient along a third axis of placement 116.

Although a patient may generally follow an anterior path followed by aposterior path (e.g., posterior right followed by posterior left and/orposterior left followed by posterior right) to place a dental appliance106 over a number of teeth, paths of placement of the dental appliance106 of the present disclosure are not so limited and can includeadditional paths.

For example, in one or more embodiments of the present disclosure, theplacement of the dental appliance 106 over the number of teeth canfollow an alternative pattern. For instance, an anterior part of adental appliance 106 can be placed over the anterior teeth of thepatient along the first axis of placement 112, then a posterior rightpart of the dental appliance 106 can be placed over the posterior rightteeth of the patient along the third axis of placement 116, and then aposterior left part of the dental appliance 106 can be placed over theposterior left teeth of the patient along the second axis of placement114. In addition, the placement of the dental appliance 106 can includea posterior left path, followed by a posterior right path, and thenfollowed by an anterior path, and/or a posterior right path, followed bya posterior left path, and then followed by an anterior path.Alternatively, the placement of the dental appliance 106 can include aposterior left path, followed by an anterior path, and then followed bya posterior right path, and/or a posterior right path, followed by ananterior path, and then followed by a posterior left path, for example.

A number of axes of placement 112, 114, 116 and/or a non-vertical axisof placement in one or more dimensions in accordance with variousembodiments of the present disclosure can be used to place a dentalappliance 106 over a number of teeth, wherein the number of teethinclude multiple undercut areas of the teeth relative to an axis ofplacement of different parts of the dental appliance over the number ofteeth. For instance, a patient with a number of retroclined incisorsand/or a number of blocked out bicuspids 103 may have an easier timeinserting a dental appliance over the patient's teeth by using multipleaxes of placement 112, 114, 116 compared to using a single axis ofplacement. A retroclined incisor can include a retroclined lower and/orupper incisor, for example. A blocked out bicuspid 103 can, forinstance, include a lingually displaced upper and/or lower premolarand/or molar.

When the appliance 106 is placed over the anterior teeth of FIG. 1B, theappliance may expand and/or widen if the configuration of the teethreceptacles in the appliance is different than the actual configurationof the teeth (as is needed in the case of sequential positioningappliances). This can make the path the other parts of the appliancemust take in order to seat different than the path of the appliance inthe otherwise unwidened state. A tooth which is excessively displaced,such as tooth 103, becomes particularly challenging to seat theappliance over, if a large discrepancy exists between the path neededand the path available as a result of the transient appliance expansionwhen the appliance is first seated in the front teeth. Arrows 114 and116 represent the additional displacement of the appliance which isneeded in order to align the respective parts of the appliance on theteeth in a way that minimizes the resistance from the undercuts present.

As illustrated in FIG. 1B, some embodiments of the present disclosurecan include an axis of placement calculated and/or estimated in light ofpotential flexion of the appliance 106 during seating and/or removal ofthe initial portion (e.g., first axis of placement 112). The one or moreaxes of placement for each part of the appliance 106 can include an archand/or with the flexion built in. The flexion can be, for example, builtin and/or presumed in the appliance and the multiple axes of placementcan account for appliance flexion. For example, calculating the axes ofplacements can include factoring for dental appliance flexion whenplaced over the number of teeth based on a material property of thedental appliance. Alternatively, in various embodiments, an appliancemay not have any flexion but may still have multiple axes of placementand/or removal.

An axis of placement of part of a dental appliance can be determined,for example, by observations of a patient and/or observations of similarpatients. A similar patient, for instance, can include a patient with asimilar and/or identical number of teeth and/or digital dental model. Asan example, a similar patient to a patient with a lingually displacedlower right premolar 103 can include a person with a lingually displacedlower right premolar and/or molar.

In a number of embodiments, an axis of placement can be calculatedand/or determined based upon data of previous placements of dentalappliances, such as observations of a patient, in combination with amethod comprising calculating an undercut area of a tooth relative to anaxis of placement of a part of a dental appliance over a number of teethand a height of contour that is defined based on the axis of placementand filling in a part of the undercut area with a virtual filler whereinthe undercut is filled to within a threshold distance from the tooththat is defined relative to the axis of placement and the height ofcontour.

The sequence of placement of the appliance (e.g., pattern of axes ofplacement and/or path of draw), in some embodiments of the presentdisclosure, can alter one or more axes of placement of parts of theappliance 106. For instance, a first axis of placement for a first partof a dental appliance 106 may affect a second axis of placement for asecond part of the dental appliance 106. In addition, the removalsequence of the dental appliance 106 may not be the same as theplacement sequence.

FIG. 2A illustrates an example of a relative height of contour 226 andan undercut area of a tooth 220 that is defined based on an estimatedaxis of placement 224 of a part of a dental appliance according to oneor more embodiments of the present disclosure. The relative height ofcontour 226 of the tooth 220, as illustrated in the embodiment of FIG.2A, can be relative to an axis of placement 224 of the part of thedental appliance. A relative height of contour 226 may not necessary bethe anatomically fattest part of a tooth relative to the tooth's longaxis. The tooth 220, as illustrated in the embodiment of FIGS. 2A and2B, can include a tooth 220 with an excessive undercut area.

In contrast, an anatomical height of contour can include a lineencircling a tooth 220 representing the greatest circumference of thetooth. The height of contour of the tooth, for instance, can encirclethe tooth in a generally horizontal manner. An undercut area of a tooth220 can include an area between the height of contour of the tooth 220and a gingiva of the tooth 222. An anatomical height of contour canpresume the tooth to be in an ideal aligned position (e.g., finalposition).

As used herein, however, a relative height of contour 226 of a tooth 220can be defined based on an axis of placement 224 of part of a dentalappliance. A height of contour 226 of a tooth 200 defined based on anaxis of placement 224 of part of a dental appliance can, for example,include a line encircling a tooth representing the greatestcircumference of the tooth relative to and/or with respect to an axis ofplacement 224 of part of a dental appliance. For instance, a greatestcircumference of a tooth 220 can include a greatest radius, bulge,convexity, and/or diameter of a tooth 220.

When the axis of placement of at least a portion of the appliancechanges (e.g., because of temporary appliance flexure during partialplacement), the relative height of contour to the unseated portions canalso change. In some instances, the change can be unfavorable, such thatthe placement of the unseated portions of the appliance can becomedifficult and/or impossible without first significantly altering theappliance and/or causing discomfort to the patient.

In accordance with one or more embodiments of the present disclosure, anundercut area of a tooth relative to an axis of placement can becalculated. For example, in the embodiment of FIG. 2A, the undercut area230 of a tooth 220 relative to an axis of placement 224 can include anarea between the height of contour 226 of the tooth 220 relative to anaxis of placement 224 and the gingiva of the tooth 222 (e.g., gum line222 of the tooth 220).

FIG. 2B illustrates an example of a virtual filler 231 filled in part ofan undercut area 230 of a digital tooth 220 according to one or moreembodiments of the present disclosure. The virtual filler 231 acts toreduce the undercut area relative to at least one axis of placement forthe appliance, so that when an appliance is made over a model with thefillers physically in place, the appliance becomes easier to place andremove along at least one axis of placement. For instance, an undercutarea 230 of a tooth 220 and/or multiple undercut areas of a number ofteeth relative to an axis of placement 224 can be filled with virtualfiller 231 on a digital dental model of the tooth 220 and/or the numberof teeth. A virtual filler 231 can include a two-dimensional (2D)virtual representation, three-dimensional (3D) virtual representation,and/or other representations of a filler material. A physical fillermaterial can be any additional material that can be added to a physicaldental mold of a patient's tooth and/or teeth to fill a space (e.g.,which can include prosthetic teeth such as pontics). The additionalmaterial can include the same and/or different material than thephysical dental mold of the patient's teeth. For example, the filler canbe integrated as part of the dental model when the model is milled orfabricated using stereolithography processes. Or the filler may be adifferent material from the dental model, such as a silicone puttycorresponding to the 3D shapes of the virtual filler 231.

In some examples of the present disclosure, the undercut area 230 of avirtual tooth 220 can be filled with a virtual filler 231 to a thresholddistance from the tooth 220 that is defined relative to the axis ofplacement 224 and the relative height of contour 226. For instance, thethreshold distance from the tooth can be defined by a line parallel 228to the axis of placement 224 and tangential to the height of contour226. A threshold distance from the tooth 220, for instance, can includea numerical value (e.g., 0.50 millimeters) representing a distance fromthe tooth 220 and/or line parallel 228 to the axes of placement 224(e.g., the line of draw for an appliance). For example, a part of theundercut area 231 of the tooth 220 can be filled in response toidentifying that a part of the calculated undercut area 230 of the tooth220 is not within the threshold distance. For instance, a part of thecalculated undercut 230 area may not be within a threshold distance fromthe tooth 220 in response to the undercut area 230 being outside (e.g.,less than, greater than) the threshold distance from the line parallel228 to the axis of placement 224 and tangential to the height of contour226.

FIG. 2C illustrates an example of a dental appliance 206 according toone or more embodiments of the present disclosure. The dental appliance206 can include an area 232 created based on use of a virtual filler(e.g., virtual filler 231 from FIG. 2B) on a digital dental model and/orfrom physical filler material added to a physical dental mold.

The dental appliance 206 can be made, for example, by thermal-forming apiece of plastic over a physical dental mold. The physical dental mold,for instance, can represent an incremental position to which a patient'steeth are to be moved. The physical dental mold can be manufactured bydownloading a Computer-aided Design (CAD) digital dental model to arapid prototyping process, such as, for example, a Computer-aidedmanufacturing (CAM) milling, stereolithography, and/or photolithography.The digital dental mold can be hollowed out or “shelled” before sent formanufacturing save on material cost, for example.

In some embodiments of the present disclosure, the dental mold caninclude a virtual and/or physical filler material added to an undercutarea of a molded tooth relative to an axis of placement of the dentalappliance 206 over the number of teeth. The filler material, forinstance, can be located to within a threshold distance of the moldedtooth.

A dental appliance 206 can be formed by layering a thermoformable sheetof material and/or multiple sheets of one or more materials over thedental mold. The materials can include a polymeric material, forinstance. Generally, the dental appliance 206 is produced and/or formedby heating the polymeric thermoformable sheet and vacuum or pressureforming the sheet over the dental mold (e.g., number of molded teeth).The shape of the sheet of material can change thickness on some portionsof the sheet as it conforms to the mold shape. A dental appliance 206can, for example, include a negative impression of the dental mold. Theappliance and/or parts thereof may be transparent, semi-transparent, oropaque in such a way as to emulate a nature tooth shade.

For instance, a dental appliance 206 formed using a dental moldincluding a filler material located in an undercut area of a moldedtooth relative to an axis of placement of the dental appliance 206 caninclude a filler space 232 between the dental appliance 206 and thetooth 220. The filler space can be created by a filler material on thedental mold. The filler material can be virtually attached to thedigital dental model and created at the same time as the dental mold(e.g., virtual filler material), and/or can be added to the physicaldental mold after the physical dental mold is formed (e.g., physicalfiller material). The filler space 232 created can include a hollowspace on an inner side of the dental appliance 206. For instance, aninner side of the dental appliance 206 can include a hollow spaceproximal to the lingual surface of a tooth 220 and/or proximal to abuccal surface of a tooth 220.

In some embodiments of the present disclosure, a dental appliance 206can include a smooth edge 234 of the dental appliance 206 proximal to agingival line of a patient 222. For instance, the smooth edge 234 can becreated by creating a smooth inward-directed (e.g., towards thetooth/gums) transition on a virtual and/or physical dental mold from thefiller material to the molded tooth and/or number of molded teeth. Thesmooth edge 234 can reduce or prevent discomfort to a patient's tissue(e.g., tongue, lips, and gum), for example.

FIG. 3 is a flow diagram illustrating an example of a method for fillingundercut areas according to one or more embodiments of the presentdisclosure. At 338, the method 336 can include creating and/or receivinga digital dental model. For example, a digital dental model can becreated from a scan of a patient's dentition and provided withcomputer-aided design and/or manufacturing systems, includingtooth-treatment systems. The digital dental model can include data for anumber of teeth. The digital dental model can include an initial digitaldental model or an intermediate position digital dental model, forexample.

At 340, the method 336 can include defining and/or determining an axisof placement of a part of a dental appliance. For example, the axis ofplacement can be calculated, determined, and/or identified fromobservations of a patient and/or one or more similar patients. Invarious embodiments of the present disclosure, axes of placement ofdifferent parts of the dental appliance can be defined.

At 342, the method 336 can include determining whether an undercut areaof a tooth that is not within a threshold distance of the tooth exists.The determination can include calculating an undercut area of a toothand/or multiple undercut areas of a number of teeth relative to an axisof placement of a part of a dental appliance and/or axes of placement ofdifferent parts of the dental appliance over the number of teeth. Anundercut area of a tooth beyond a threshold distance can include a partof a calculated undercut area of a tooth that is not within a thresholddistance from a line parallel to the axis of placement and tangential tothe height of contour.

A threshold distance from a line parallel to the axis of placement andtangential to the relative height of contour can include a maximumdistance and/or a minimum distance from the line parallel to the axis ofplacement and tangential to the relative height of contour. For example,an undercut area of a tooth that is over a maximum threshold area can bedetermined. This can represent an area of an appliance that may beexcessively retentive relative to a particular axis of placement. Amaximum threshold area can include an undercut area of a tooth and/orpart of an undercut area of the tooth that is greater than a thresholddistance from the line (e.g., a maximum threshold distance)

Alternatively and/or in addition, an undercut area of a tooth that isnot at least a minimum threshold area may be determined. This canrepresent an area of an appliance which may be insufficiently retentiverelative to a particular axis of placement. A minimum threshold area caninclude an undercut area of a tooth and/or part of a tooth that is lessthan a threshold distance from the line parallel to the axis ofplacement and tangential to the relative height of contour (e.g.,minimum threshold distance). In such a situation, the insufficientundercut may be supplemented by the addition of an artificial undercutsuch as dental protrusions attached to the surfaces of the teeth.

In a number of embodiments, identifying that a part of the calculatedundercut area of the tooth is not within the threshold distance (e.g.,above and/or below) can be included in any one of, or any combinationof: a method comprising calculating an undercut area of a tooth relativeto an axis of placement of a part of a dental appliance over a number ofteeth and a relative height of contour that is defined based on the axisof placement (e.g., line of draw) and filling in a part of the undercutarea with a virtual filler wherein the undercut area is filled to withina threshold distance from the tooth that is defined relative to the axisof placement of a part of the dental appliance over the number of teethand a relative height of contour and/or supplementing an insufficientundercut area with an artificial undercut; the method, wherein the axisof placement of the dental appliance defines an estimated path ofplacement of the part of the dental appliance over the number of teeth;the method, wherein calculating the undercut area of the tooth furtherincludes filling in the part of the undercut area with a virtual fillerwherein the undercut is filled and/or an artificial undercut isintroduced to within a threshold distance from the tooth that is definedby a line parallel to the axis of placement and tangential to therelative height of contour; and, the method, including calculatingmultiple undercut areas of the number of teeth relative to axes ofplacement of different parts of the dental appliance over the number ofteeth.

In response to determining that no undercut area exists, the method 336can be complete 344. In response to determining that an undercut areabeyond a threshold exists, the method 336 can include determiningwhether the undercut area is beyond a minimum threshold and/or a maximumthreshold 345. Determining can include identifying if an undercut areaof the tooth is greater or less than a threshold distance from the line,for instance. An undercut area greater than a threshold distance (e.g.,maximum threshold area and/or distance) can include an excessiveundercut area. An undercut area less than a threshold distance (e.g.,minimum threshold area and/or distance) can include an insufficientundercut area.

In response to determining that an excessive undercut area exists (e.g.,greater than a maximum threshold), the method 336 can include addingvirtual filler to the undercut area of a tooth 346. Adding virtualfiller can, for example, include filling in a part of the undercut areaand/or part of each of the multiple undercut areas with virtual fillerwherein the undercut area of the tooth and/or each tooth is filled towithin a threshold distance that is defined relative to the one or moreaxes of placement and the height of contour nearest the tooth and/oreach tooth. For example, adding virtual filler can include adding arepresentation of a filler material to an undercut area of a tooth towithin a threshold distance from the tooth that is defined by a lineparallel to the axis of placement and tangential to the height ofcontour. In various embodiments of the present disclosure, analternative response can include determining that artificial undercutsthat are planned as part of the treatment plan for specific toothmovements (e.g., rotation, inclination, and/or angulation) may bealtered to reduce the amount of undercut relative to the height ofcontour relative to the axis of placement.

In response to determining that an insufficient undercut area exists(e.g, less than a minimum threshold), the method 336 can include addingand/or creating an artificial undercut to the undercut area of a tooth347. An artificial undercut are can include a pressure point and/or anattachment. A pressure point, as used herein, can include virtual and/orphysical removal of certain areas of the reference model. An attachment,as used herein, can include a protruding apparatus that can be added(e.g., as further discussed in FIG. 6B).

In various embodiments of the present disclosure, one or more excessiveundercut areas and one or more insufficient undercut areas can exist.For example, the one or more excessive undercut areas and the one ormore insufficient undercut areas can be identified and/or located on thesame tooth and/or separate teeth.

In some embodiments of the present disclosure, the method 336 caninclude determining if a rough edge exists on the digital dental model348. For instance, a rough edge can include an edge of the dentalappliance proximal to a gingival line of a patient that is not convexrelative to a tooth and/or tissue of a patient (e.g., inward facingtowards the teeth/gums) and/or not within a threshold distance of thegingival line of the patient.

In response to determining no rough edges exist, the method 336 can becomplete 350. In response to determining a rough edge and/or multiplerough edges exist, the method 336 can include defining an edge of thedental appliance proximal to a gingival line of a patient 352. Forinstance, an edge of the dental appliance proximal to the gingival lineof a patient can include an edge near, touching, and/or close to thegingival line of the patient. A rough edge can be, for instance, createdby the virtual filler and/or an artificial undercut, among othersurfaces.

At 354, the method can include creating a smooth transition of thevirtual filler and/or a gap created by the artificial undercut (e.g., asdiscussed further in FIG. 6B) to the defined edge. For instance, asmooth transition can include an accommodation in the dental appliancethat wraps around and/or near a surface of the tooth. The surface of thetooth, for instance, can include a buccal and/or lingual surface. Thesmooth transition of the virtual filler and/or gap created by theartificial undercut to the defined edge, for example, can include aconvex shape relative to the patient's teeth and/or tissue.

In some embodiments of the present disclosure, creating a smooth edge ofthe virtual filler can be included in any one of, or any combination of:a method comprising calculating an undercut area of a tooth relative toan axis of placement of a part of a dental appliance over a number ofteeth and a height of contour that is defined based on the axis ofplacement and filling in a part of the undercut area with a virtualfiller wherein the undercut area is filled to within a thresholddistance from the tooth that is defined relative to the axis ofplacement (e.g., line of draw) of a part of the dental appliance overthe number of teeth and a height of contour; the method, wherein theaxis of placement of the dental appliance defines an estimated path ofplacement of the part of the dental appliance over the number of teeth;the method, wherein calculating the undercut area of the tooth furtherincludes filling in the part of the undercut area with a virtual fillerwherein the undercut is filled to within a threshold distance from thetooth that is defined by a line parallel to the axis of placement andtangential to the height of contour; and, the method, includingcalculating multiple undercut areas of the number of teeth relative toaxes of placement of different parts of the dental appliance over thenumber of teeth. In the event of insufficient undercut according to aminimum threshold, an artificial undercut can be added either manuallyor automatically, through the addition of artificial undercuts such asprotrusions to be bonded into place onto the teeth by the practitionerand/or virtual removal of material from the appliance.

As an example, creating a smooth edge of virtual filler can be includedin a method comprising calculating one or more axes of placement of adental appliance over a number of teeth based upon data of previousplacements of dental appliances, calculating an undercut area of a toothrelative to the one or more axis of placement of a part of the dentalappliance over the number of teeth (e.g., the calculated one or moreaxis of placement of the dental appliance) and a height of contour thatis defined based on the axis of placement, and filling in a part of theundercut area with a virtual filler wherein the undercut area is filledto within a threshold distance from the tooth that is defined relativeto the axis of placement of a part of the dental appliance over thenumber of teeth and a height of contour.

FIG. 4 illustrates an example computing device readable medium 456having executable instructions that can be executed by a processor toperform a method according to one or more embodiments of the presentdisclosure. For instance, a computing device 458 can have a number ofcomponents coupled thereto. The computing device 458 can include aprocessor 460 and a memory 464. The memory 464 can have various types ofinformation including data 466 and executable instructions 468, asdiscussed herein.

The processor 460 can execute instructions 468 that are stored on aninternal or external non-transitory computer device readable medium(CRM). A non-transitory CRM, as used herein, can include volatile and/ornon-volatile memory. Volatile memory can include memory that dependsupon power to store information, such as various types of dynamic randomaccess memory (DRAM), among others. Non-volatile memory can includememory that does not depend upon power to store information.

Memory 464 and/or the processor 460 may be located on the computingdevice 458 or off the computing device 458, in some embodiments. Assuch, as illustrated in the embodiment of FIG. 4, the computing device458 can include a network interface 462. Such an interface 462 can allowfor processing on another networked computing device, can be used toobtain information about the patient, and/or can be used to obtain dataand/or executable instructions for use with various embodiments providedherein.

As illustrated in the embodiment of FIG. 4, the computing device 458 caninclude one or more input and/or output interfaces 470. Such interfaces470 can be used to connect the computing device 458 with one or moreinput and/or output devices 472, 474, 476, 478, 480.

For example, in the embodiment illustrated in FIG. 4, the input and/oroutput devices can include a scanning device 472, a camera dock 474, aninput device 476 (e.g., a mouse, a keyboard, etc.), a display device 478(e.g., a monitor), a printer 480, and/or one or more other inputdevices. The input/output interfaces 470 can receive executableinstructions and/or data, storable in the data storage device (e.g.,memory), representing a digital dental model of a patient's dentition.

In some embodiments, the scanning device 472 can be configured to scanone or more physical dental molds of a patient's dentition. In one ormore embodiments, the scanning device 472 can be configured to scan thepatient's dentition and/or dental appliance directly. The scanningdevice 472 can be configured to input data into the computing device458.

In some embodiments, the camera dock 474 can receive an input from animaging device (e.g., a 2D or 3D imaging device) such as a digitalcamera, a printed photograph scanner, and/or other suitable imagingdevice. The input from the imaging device can, for example, be stored inmemory 464.

The processor 460 can execute instructions to provide a visualindication of a treatment plan, an axis of placement, and/or an undercutarea of a tooth relative to an axis of placement on the display 478. Thecomputing device 458 can be configured to allow a treatment professionalor other user to input treatment goals. Input received can be sent tothe processor 460 as data 466 and/or can be stored in memory 464.

Such connectivity can allow for the input and/or output of data and/orinstructions among other types of information. Some embodiments may bedistributed among various computing devices within one or more networks,and such systems as illustrated in FIG. 4, can be beneficial in allowingfor the capture, calculation, and/or analysis of information discussedherein.

The processor 460, in associated with the data storage device (e.g.,memory 464), can be associated with the data 466. The processor 460, inassociation with the memory 464, can store and/or utilize data 466and/or execute instructions 468 for filling undercut areas of teethrelative to axes of placement different parts of a dental appliance.Such data can include the digital dental model and/or a defined axis ofplacement.

The processor 460 coupled to the memory 464 can cause the computingdevice 458 to perform a method including, for example, calculating anundercut area of a tooth relative to an axis of placement of a part of adental appliance over a number of teeth and a height of contour based onthe axis of placement. In various embodiments of the present disclosure,the processor 460 coupled to the memory 464 can cause the computingdevice to perform the method including calculating multiple undercutareas of the number of teeth relative to axes of placement of differentparts of the dental appliance over the number of teeth. For instance,the multiple axes of placement can include an anterior line of draw, aposterior left line of draw, a posterior right line of draw, and/or anycombination thereof.

In accordance with one or more embodiments of the present disclosure, anaxes of placement including an anterior line of draw, a posterior leftline of draw, and a posterior right line of draw can be included in anyone of, or any combination of: a method comprising calculating multipleundercut areas of a number of teeth relative to axes of placement ofdifferent parts of a dental appliance over a number of teeth and filingin a part of the undercut area with a virtual filler wherein theundercut of each tooth is filled to within a threshold distance that isdefined relative to the one or more axis of placement and the relativeheight of contours nearest the tooth; the method, wherein calculatingmultiple undercut areas includes calculating undercut areas relative toa first axis of placement of a first part of the dental appliance over anumber of teeth and a height of contour that is defined based on thefirst axis of placement, and a second axis of placement of a second partof the dental appliance over a number of teeth and a height of contourthat is defined based on the second axis of placement; the method,wherein the first axis of placement corresponds to an anterior part ofthe dental appliance and the second axis of placement corresponds to aposterior part of the dental appliance; the method, wherein the firstaxis of placement corresponds to an anterior part of the dentalappliance and the second axis of placement corresponds to one of aposterior left part of the dental appliance and a posterior right partof the dental appliance.

In some examples, an axes of placement including an anterior line ofdraw, a posterior left line of draw, and a posterior right line of drawcan be included in any one of, or any combination of: a methodcomprising calculating multiple undercut areas of a number of teethrelative to axes of placement of different parts of a dental applianceover a number of teeth and filing in a part of the undercut area with avirtual filler wherein the undercut of each tooth is filled to within athreshold distance that is defined relative to the one or more axis ofplacement and the relative height of contours nearest the tooth; themethod, wherein calculating multiple undercut areas includes calculatingundercut areas relative to a first axis of placement of a first part ofthe dental appliance over a number of teeth and a height of contour thatis defined based on the first axis of placement, a second axis ofplacement of a second part of the dental appliance over a number ofteeth and a height of contour that is defined based on the second axisof placement, and a third axis of placement of a third part of thedental appliance over a number of teeth and a height of contour that isdefined based on the third axis of placement; and, the method, whereinthe first axis of placement corresponds to an anterior part of thedental appliance, the second axis of placement corresponds to aposterior left part of the dental appliance, and the third axis ofplacement corresponds to a posterior right part of the dental appliance.

The processor 460 coupled to the memory 464 can cause the computingdevice 458 to perform a method including filling in a part of theundercut area with a virtual filler wherein the undercut is filled towithin a threshold distance from the tooth that is defined relative tothe axis of placement and the height of contour.

In some embodiments of the present disclosure, the processor 460 coupledto the memory 464 can cause the computing device 458 to perform a methodincluding calculating an axis of placement of part of the dentalappliance over the number of teeth based upon data of previousplacements of dental appliances. For instance, calculating an axis ofplacement can include defining the axis of placement using an undercutdraft. An undercut draft can include minimizing a number of geometricshapes perpendicular to an axis of placement. The minimized number ofgeometric shapes can be compared to a threshold number of geometricshapes. A geometric shape, for instance, can include a triangle, arectangle, and/or a quadrilateral, among many other geometric shapes.

The data of previous placements of dental appliances can include data ofone or more axes of placement of dental appliances over similarpatient's teeth. For instance, a similar patient can include a patientwith a similar arranged number of teeth of patients and/or similarinitial digital dental models. Axes of placement of dental appliancesover similar patient's teeth can be used as an initial axis of placementover the patient number of teeth and the number of geometric shapes canbe minimized, for instance. The data can also include inputs from atreatment professional and/or other user of observed axes of placementsof the patient and/or similar patients. The input from treatmentprofessional and/or other user can be input by the treatmentprofessional and/or other user on the computing device 458 and/or aseparate computing device. The separate computing device and thecomputing device 458 can communicate using the network interface 462,for instance.

In a number of embodiments of the present disclosure, calculating anaxis of placement of the dental appliance over the number of teeth basedupon data of previous placements of dental appliances can be included inany one of, or any combination of: a method comprising calculating anundercut area of a tooth relative to an axis of placement of a part of adental appliance over a number of teeth and a height of contour that isdefined based on the axis of placement and filling in a part of theundercut area with a virtual filler wherein the undercut area is filledto within a threshold distance from the tooth that is defined relativeto the axis of placement of a part of the dental appliance over thenumber of teeth and a height of contour; the method, wherein the axis ofplacement of the dental appliance defines an estimated path of placementof the part of the dental appliance over the number of teeth; themethod, wherein calculating the undercut area of the tooth furtherincludes filling in the part of the undercut area with a virtual fillerwherein the undercut is filled to within a threshold distance from thetooth that is defined by a line parallel to the axis of placement andtangential to the height of contour; and, the method, includingcalculating multiple undercut areas of the number of teeth relative toaxes of placement of different parts of the dental appliance over thenumber of teeth.

FIG. 5A illustrates an example of a method for filling excessiveundercut areas on a dental mold according to one or more embodiments ofthe present disclosure. At 584, the method 582 can include creating aset of molded teeth from a digital model of a number of teeth of apatient. A digital model, for example, can include an initial digitaldental model and/or intermediate digital dental model. A dental mold canbe formed in accordance with a unique treatment file that identifies apatient, a stage of a treatment plan, the digital model of the number ofteeth, and/or whether the dental mold is of the upper and/or lowerdental arch.

In some embodiments, a treatment file can be accessed by a rapidprototyping apparatus machine, such as a SLA or printing, to form and/orcreate the dental mold. The result of the dental mold can include a setof molded teeth. The set of molded teeth can include at least a replicaof the number of teeth of the patient. The dental mold can be used tomake a dental appliance, for example, by creating a negative impressionof the dental mold using polymeric sheets of material and vacuum formingthe sheets over the dental mold, as discussed above.

At 586, the method 582 can include adding a filler material to a firstnumber of the molded teeth among the set of molded teeth, wherein thefiller material is located in an undercut area of the first number ofmolded teeth relative to an axis of placement of a dental appliance overthe number of teeth. The filler material, for example, can be added tothe first number of molded teeth among the set of molded teeth afterand/or during formation of the dental mold. For instance, once thedental mold is formed, the filler material can be added over the firstnumber of molded teeth. The filler material can include the samematerial as the molded teeth and/or a different material. The fillermaterial can create a negative image of the virtual filler on the dentalappliance.

In various embodiments of the present disclosure, the method 582 caninclude adding virtual filler material to the first number of moldedteeth among the number of molded teeth of a digital model of the numberof teeth to produce the dental mold. For instance, a virtual filler canbe added to the digital model of the first number of teeth. The virtualfiller can represent the physical filler material to be added. Thephysical dental mold formed using a rapid prototyping apparatus machinecan include the physical filler material located in parts of theundercut areas of the first number of molded teeth, for example.

In accordance with some embodiments of the present disclosure, themethod 582 can include creating a smooth transition from the fillermaterial to the first number of molded teeth. The smooth transition caninclude a smooth transition to a gingival line of the number of moldedteeth, for instance.

In various embodiments of the present disclosure, the method 582 caninclude adding filler material to a region of the dental mold to, forexample, reduce retention of the dental appliance in the region. Forinstance, the region of the dental mold can include one of an anteriorregion, posterior left region, and/or a posterior right region.

In some embodiments, adding a filler region to a region of the dentalmold to reduce retention of the dental appliance can be included in anyone of, or any combination of: a method of making a dental moldcomprising creating a set of molded teeth from a digital dental model ofa number of teeth of a patient and adding a filler material to a firstnumber of the molded teeth among the set of molded teeth, wherein thefiller material is located in an undercut area of the first number ofmolded teeth relative to an axis of placement of a dental appliance overthe number of teeth; the method, wherein at least one of the firstnumber of molded teeth further includes at least one of an incisor andbicuspid; and, the method, including creating a smooth transition fromthe filler material to the number of molded teeth.

In some embodiments, an artificial undercut can be introduced in theevent that the undercut area value falls below a minimum threshold. Anundercut area of a tooth below a minimum threshold can include aninsufficient undercut area. For instance, an artificial undercut can beadded to a second number of the molded teeth among the molded teeth,wherein the second number of teeth have an undercut area beyond aminimum threshold (e.g., below the threshold). An undercut area beyond aminimum threshold can include an undercut area of a tooth and/or part ofa tooth that is less than a threshold distance from the line parallel tothe axis of placement and tangential to the relative height of contour(e.g., minimum threshold distance).

FIG. 5B illustrates an example of a method for filling insufficientundercut areas on a dental mold according to one or more embodiments ofthe present disclosure. The method 583 can include filling insufficientundercut areas of molded teeth with an artificial undercut. At 585, themethod 583 can include creating a set of molded teeth from a digitalmodel of a number of teeth of a patient.

At 587, the method 583 can include adding an artificial undercut to afirst number of the molded teeth among the set of molded teeth, whereinthe artificial undercut is located in an undercut area of the firstnumber of molded teeth relative to an axis of placement of the dentalappliance over the number of teeth. The artificial undercut, as usedherein, can include a virtual and/or physical protrusion added to thefirst number of molded teeth among the number of molded teeth of adigital dental model, and/or virtual and/or physical removal of materialfrom the appliance. For instance, the virtual protrusion can be added tothe digital model of the first number of teeth. The virtual protrusioncan represent a physical protrusion (e.g., an attachment) to be added.The virtual removal of material can include a representation of materialremoved from the dental appliance (e.g. the digital model). A virtualand/or physical removal of material from the appliance can includecreating a pressure point on the dental appliance. A dental appliancecreated from the digital model including virtual material removed caninclude pressure points at the location of the virtually removedmaterial (e.g., located in the undercut areas of the first and/or secondnumber of molded teeth).

The artificial undercut can be added to each of the first number ofmolded teeth, wherein the artificial undercut of each tooth is within athreshold distance from the line that is defined relative to the one ormore axes of placement of the dental appliance. Thereby, the artificialundercut can include a virtual and/or physical protrusion and/or avirtual and/or physical pressure point of the appliance that increasesthe undercut area of a tooth in at least one dimension until thethreshold distance is present to ensure adequate appliance retention.

In various embodiments of the present disclosure, a method for fillingundercut areas on a dental mold can include adding filler material to afirst number of molded teeth among the set of molded teeth, in additionto adding an artificial undercut to a second number of molded teethamong the set of molded teeth. The first number of molded teeth caninclude representations of teeth with excessive undercut areas. Thesecond number of molded teeth can include representations of teeth withinsufficient undercut areas.

FIG. 6A illustrates an example of a tooth 688 with an insufficientundercut area 630 according to one or more embodiments of the presentdisclosure. An insufficient undercut area 630 of a tooth 688 can includean undercut area 630 that is not sufficient for retention of a dentalappliance.

In accordance with some embodiments of the present disclosure, a tooth688 can be identified with an insufficient undercut area 630. Forexample, an insufficient undercut area 630 can be identified bycalculating that part of an undercut area 631 relative to a lineparallel 628 to an axis of placement 624 is less than a thresholddistance from the tooth 688. An insufficient undercut area 630 of thetooth 688 can include an area of the tooth 688 between a height ofcontour 626 of the tooth 688 relative to an axis of placement 624 of apart of a dental appliance and a gingivia of the tooth 622 (e.g., gumline of the tooth 688).

Part of an undercut area 631 of a tooth may be beyond than the thresholddistance from the tooth 688, for instance, if part of the undercut area631 is closer than the threshold distance to a line parallel 628 to anaxis of placement 624 and tangential to the height of contour 626 of thetooth. For example, an undercut area 630 of a tooth 688 may beinsufficient if the distance 690 (e.g., distance α) between part of theundercut area 631 of the tooth 688 and the line parallel 628 to an axisof placement 624 is less than the threshold distance (e.g., minimumthreshold distance and/or area).

FIG. 6B illustrates an example of a dental appliance 606 according toone or more embodiments of the present disclosure. The dental appliance606 can include an attachment 694 created to retain the dental appliance606 onto the number of teeth (e.g., tooth 688).

An attachment 694, for instance, can include a ridge 692 on the dentalappliance 606 used to retain the dental appliance 606 onto a tooth 688with an insufficient undercut area (e.g., as illustrated by 630 of FIG.6A). An attachment 694 can be added, for instance, to create greaterretention of a part of the dental appliance 606 in a particulardirection (e.g., greater degree of fit of the dental appliance). Theappliance 606 can include a physical protrusion 698 extending a surfaceof the tooth 688 (e.g., lingually).

An attachment 694 can include an apparatus added to the tooth. Anattachment 694 can be added to a tooth 688 that has an identifiedinsufficient undercut area. For instance, the attachment 694 can beadded directly to the patient's tooth 688. The attachment 694 caninclude an attachment sub-device with a small base extending across amesial-distal and/or gingiva-crown of the tooth 688. The attachment 694can be bonded to any surface of the tooth 688, including a lingualsurface which would allow the attachment 694 to be more unnoticeable toothers. Shape and design considerations can reduce or prevent anyirritation to the contacting tissues, such as the tongue, inner lip,and/or inner cheek. The attachment 694 can be designed to work with aremovable dental appliance (e.g., 606). For instance, the attachment 694can provide friction against a ridge 692 of the dental appliance 606 toincrease retention of the dental appliance 606.

The ridge 692, in combination with the attachment 694, may cause thedental appliance 606 to flare from the tooth 688 of the patient. Theflare, for instance, can include a hollow space and/or gap (e.g., gap696) between the gingival line of the patient 622 and an edge of thedental appliance 606 proximal to the gingival line 622 of the patient.Tissue near the flare, such as a tongue, inner lip, and/or inner cheekof a patient, can become trapped in the gap and become inflamed and/orirritated. Thereby, the edge of the appliance can create and/or cause arough edge on the dental appliance 606 (e.g., edge of the dentalappliance proximal to the gingival line of the patient 622).

In accordance with one or more embodiments of the present disclosure, asillustrated by FIG. 6B, a dental appliance 606 with a ridge 692 caninclude an inward-facing smooth edge 698 from the hollow space and/orgap 696 created by the ridge 692 to the gingiva of a tooth 622 and/orthe tooth 688. An inward-facing smooth edge 698 can be created, forexample, by creating a smooth transition on a virtual and/or physicaldental mold from a hollow space and/or gap 696 caused by a ridge 692and/or attachment 694 to the molded tooth and/or number of molded teeth(e.g., tooth 688). For instance, a distance of the smooth transition(e.g., smooth edge 698) can be equal and/or proportional to a depth ofthe ridge 692 (e.g., the depth the ridge 692 protrudes toward a surfaceof the tooth 688). The smooth edge 698 can reduce and/or preventdiscomfort to a patient's mouth (e.g., tongue, lips, and gums), forexample, by reducing and/or preventing a rough edge on the dentalappliance 606 created and/or caused by the ridge 692 and/or attachment694. The inward-facing smooth edge 698 can be contoured toward the tooth688 and/or gums 622, for example.

Although specific embodiments have been illustrated and describedherein, those of ordinary skill in the art will appreciate that anyarrangement calculated to achieve the same techniques can be substitutedfor the specific embodiments shown. This disclosure is intended to coverany and all adaptations or variations of various embodiments of thedisclosure.

It is to be understood that the above description has been made in anillustrative fashion, and not a restrictive one. Combination of theabove embodiments, and other embodiments not specifically describedherein will be apparent to those of skill in the art upon reviewing theabove description.

The scope of the various embodiments of the disclosure includes anyother applications in which the above structures and methods are used.Therefore, the scope of various embodiments of the disclosure should bedetermined with reference to the appended claims, along with the fullrange of equivalents to which such claims are entitled.

In the foregoing Detailed Description, various features are groupedtogether in example embodiments illustrated in the figures for thepurpose of streamlining the disclosure. This method of disclosure is notto be interpreted as reflecting an intention that the embodiments of thedisclosure require more features than are expressly recited in eachclaim.

Rather, as the following claims reflect, inventive subject matter liesin less than all features of a single disclosed embodiment. Thus, thefollowing claims are hereby incorporated into the Detailed Description,with each claim standing on its own as a separate embodiment.

What is claimed is:
 1. A non-transitory computing device readable mediumhaving executable instructions that can be executed by a processor tocause a computing device to perform a method, comprising: calculating anundercut area of a virtual tooth included in a digital model of a numberof virtual teeth relative to an axis of placement of a part of a virtualdental appliance over the number of virtual teeth and a height ofcontour that is defined based on the axis of placement; determiningwhether the undercut area is less than a minimum threshold distance fromthe axis of placement, wherein the minimum threshold distance is lessthan a threshold distance from the virtual tooth, the threshold distancedefined relative to the axis of placement and the height of contour; andadding a virtual protrusion to the virtual tooth of the number ofvirtual teeth in response to the undercut area being less than thethreshold distance; and providing the virtual protrusion for a physicalprotrusion on a physical dental appliance.
 2. The non-transitorycomputing device readable medium of claim 1, wherein the virtualprotrusion is configured to retain the virtual dental appliance onto thenumber of virtual teeth.
 3. The non-transitory computing device readablemedium of claim 1, wherein the virtual protrusion is within thethreshold distance from a line that is defined relative to the axis ofplacement of the virtual dental appliance.
 4. The non-transitorycomputing device readable medium of claim 1, wherein the virtualprotrusion includes a base.
 5. The non-transitory computing devicereadable medium of claim 1, wherein adding the virtual protrusion to thevirtual tooth includes attaching the virtual protrusion to the virtualtooth via a base of the virtual protrusion.
 6. The non-transitorycomputing device readable medium of claim 1, wherein the instructionsare executed to add the virtual protrusion to a lingual surface of thevirtual tooth.
 7. The non-transitory computing device readable medium ofclaim 1, wherein the instructions are executed to perform the methodincluding creating a ridge in the virtual dental appliance toaccommodate the virtual protrusion.
 8. The non-transitory computingdevice readable medium of claim 7, wherein the virtual protrusion isconfigured to provide friction against the ridge in the virtual dentalappliance to retain the virtual dental appliance onto the number ofvirtual teeth.
 9. The non-transitory computing device readable medium ofclaim 7, wherein the instructions are executed to perform the methodincluding defining an inward-facing smooth edge of the virtual dentalappliance proximal to a gingival line of the number of virtual teeth asa result of the creation of the ridge.
 10. The non-transitory computingdevice readable medium of claim 9, wherein the instructions are executedto define the inward-facing smooth edge of the virtual dental applianceto contour towards the virtual tooth.
 11. A method of making a dentalmold, comprising: receiving a digital model of a number of teeth of apatient; creating a set of molded teeth from the digital model of thenumber of teeth of the patient; determining whether an undercut area ofthe set of molded teeth is less than a minimum threshold distancerelative to an axis of placement of a dental appliance over a number ofmolded teeth; adding a protrusion to a tooth of the number of moldedteeth; and creating a physical dental appliance using the number ofmolded teeth, wherein the physical dental appliance includes a ridgesuch that the protrusion provides friction against the ridge to retainthe physical dental appliance onto the number of molded teeth.
 12. Themethod of claim 11, wherein creating the physical dental applianceincludes creating an inward-facing smooth edge of the physical dentalappliance, wherein the inward-facing smooth edge is located proximal toa gingival line of the number of molded teeth.
 13. The method of claim12, wherein creating the inward-facing smooth edge includes creating asmooth transition on a physical dental mold.
 14. The method of claim 13,wherein the smooth transition is equal to a depth of the ridge of thedental appliance.
 15. The method of claim 13, wherein the smoothtransition is proportional to a depth of the ridge of the dentalappliance.
 16. The method of claim 11, wherein the method includescalculating the axis of placement of the dental appliance over thenumber of molded teeth based upon data of previous placements of dentalappliances.
 17. A computing device implemented method, comprising:calculating multiple undercut areas of a sub-set of teeth of a number ofteeth relative to axes of placement of different parts of a dentalappliance over the number of teeth; determining whether each of themultiple undercut areas are less than a minimum threshold distancerelative to each respective axis of placement of each tooth of thesub-set of the number of teeth, wherein each minimum threshold distanceis less than a threshold distance from each tooth; adding a protrusionto each tooth of the sub-set of the number of teeth; and creating aphysical dental appliance for the number of teeth, wherein the physicaldental appliance includes a ridge such that the protrusion of each toothprovides friction against the ridge to retain the physical dentalappliance onto the number of teeth.
 18. The method of claim 17, whereincalculating the multiple undercut areas includes calculating undercutareas relative to: a first axis of placement of a first part of thedental appliance over the number of teeth and a height of contour thatis defined based on the first axis of placement; and a second axis ofplacement of a second part of the dental appliance over the number ofteeth and a height of contour that is defined based on the second axisof placement.
 19. The method of claim 18, wherein the first axis ofplacement corresponds to an anterior part of the physical dentalappliance and the second axis of placement corresponds to a posteriorpart of the physical dental appliance.
 20. The method of claim 18,wherein the first axis of placement corresponds to an anterior part ofthe physical dental appliance and the second axis of placementcorresponds to one of a posterior left part of the physical dentalappliance and a posterior right part of the physical dental appliance.